During the production of crude oil, it is necessary to pump the crude from the wellbores into a battery of crude oil storage tanks, sometimes called a tank farm, where the crude oil is accumulated until a sufficient quantity is on hand to justify transportion through the pipeline to the refinery. From time to time, the individual crude storage tanks must be gauged in order to determine the amount of crude contained therewithin.
The oilfield hand, or workman, who gauges the crude stock tanks of the tank farm is called a Gauger or a Pumper. The gauger has a sampling apparatus called a thief which he lowers into the tank to a predetermined depth and then trips the thief, whereupon the tank liquid fills the thief. When the thief is brought out of the tank, a tank sample at a specified depth is available for subsequent analysis. At the same time, the depth of the tank is gauged or measured.
The top of the stock tank is provided with an opening, usually in the form of a hatch, and when the lid of the hatch is opened, the gauger sometimes is rendered unconscious because of inhalation of hydrogen sulfide, which often is fatal if the gauger does not immediately recognize his plight and remove himself from proximity of the deadly gas.
Hydrogen sulfide is very corrosive, and when it escapes from the interior of the tank and admixes with moisture and atmospheric oxygen, the exterior of the tank is rapidly eaten away by the corrosive action of the hydrogen sulfide.
Accordingly, it would be desirable to eliminate the above recited dangers associated with the deadly hydrogen sulfide contained within the vapor space of a stock tank. Such a desirable expedient would necessarily have to include means by which the gauger could continue to sample the tank. Apparatus which achieves this desirable goal is the subject of the instant invention.